Methods and arrangements for moving bulk materials in conventional trains, trucks, conveyor belts, aerial tramways or as a slurry in a pipeline are well known and are typically used in various industries because of site-specific needs or experience. In the minerals and aggregate industries, for example, bulk materials are moved from mining or extraction sites to a process facility for upgrading or sizing. Trucks had been the system of choice for many years for moving bulk materials. Trucks were enlarged for off-road vehicles because of their efficient transport of bulk materials and increased capacity. These vehicles, however, are limited to site specific applications and are provided at a high capital cost. Major off-road trucks have evolved that require very wide roadways for passing each other, are not energy efficient per ton-mile of material transported, have limited hill climbing ability, and are dangerous because of potential of operator error as well as being environmentally unpleasant neighbors.
Trains have been used for many years for bulk material transport in hopper cars. Because of low friction, the use of free rolling iron or steel wheels on steel tracks they are very efficient users of energy but are limited in capacity relative to the drivers or locomotives required. Large tonnage long trains use multiple drivers that are heavy units, which dictate the weight of rail and ballast requirements. All railroads must be designed for the weight of the drivers or locomotives included fuel, not the combination of car plus loads, which are significantly less. The drivers need to be of sufficient weight so that the rotary drive tire makes contact with the stationary rail and must have sufficient friction to produce forward or reverse movement of what will include heavily loaded cars. The inclination capable of conventional railroad systems is limited to the friction between the weighted drive wheels and track. Rail cars are individual units that each has to be loaded in a batch process, one car at a time. Bulk materials can be unloaded from hopper cars by opening bottom dump hatches or can be individually rotated to dump out of the top. Spotting cars for both loading and unloading is time consuming and labor intensive.
Although moving from one location to another may be cost effective, the added cost of batch loading and unloading stages in shorter distance transports reduces the rail transport cost effectiveness. With normal single dual track train systems only one train can be used on a system at a time.
Conveyor belts have been used for many years to move bulk materials. A wide variety of conveyor belt systems exist that can move practically every conceivable bulk material. Very long distance single belt runs are very capital cost intensive and are subject to catastrophic failure when a belt tears or rips, typically shutting down the entire system and dumping the carried load, requiring cleanup. Conveyor belts are relatively energy efficient but can require high maintenance because of an inherent problem of multiple idler bearings requiring constant checking and replacement. Short distance conveyor belts are commonly used in dry or clamp transport of almost all types of materials. Because conveyor belts are very flexible and desirably operated over fairly flat terrain, they are not efficient at transporting moderately high solids slurry where water and fines can accumulate in low spots and spill over the side creating wet spilled slurry handling problems.
Some bulk materials can be transported in pipelines when mixed with water to form slurry that is pushed or pulled with a motor driven pump impeller in an airless or flooded environment. The size of the individual particles that are present in the bulk materials dictates the transport speed necessary to maintain movement. For example, if large particles are present then the velocity must be high enough to maintain movement by saltation or skidding along the bottom of the pipe of the very largest particles. Because pipelines operate in a dynamic environment, friction is created with the stationary pipe wall by a moving fluid and solid mass. The higher the speed of the moving mass the higher the friction loss at the wall surface requiring increased energy to compensate. Depending on the application, the bulk material has to be diluted with water initially to facilitate transport and dewatering at the discharge end.
Light rail, narrow gage railroads for transporting bulk material from mines and the like is known as described by way of example with reference to U.S. Pat. No. 3,332,535 to Hubert et al. wherein a light rail train made up of several cars is propelled by drive wheels and electric motors combinations, dumping over an outside loop. By way of further example, U.S. Pat. No. 3,752,334 to Robinson, Jr. et al. discloses a similar narrow gage railroad wherein the cars are driven by an electric motor and drive wheels. U.S. Pat. No. 3,039,402 to Richardson describes a method of moving railroad cars using a stationary friction drive tire.
While the above described transport systems and methods have specific advantages over conventional systems, each is highly dependent upon a specific application. It has become apparent that increases in labor, energy and material costs plus environmental concerns that alternate transport methods need to be applied that are energy and labor efficient, quiet, non-polluting, and esthetically unobtrusive. US Patent Publications US 2003/0226470 to Dibble et al. for “Rail Transport System for Bulk Materials”, US 2006/0162608 to Dibble for “Light Rail Transport System for Bulk Materials”, and U.S. Pat. No. 8,140,202 to Dibble describe a light rail train utilizing an open semi-circular trough train with drive stations, the disclosures of which are herein incorporated by reference in their entirety. Such a light rail system offers an innovative alternative to the above mentioned material transport systems and provides for the transport of bulk materials using a plurality of connected cars open at each end except for the first and last cars, which have end plates. The train forms a long open trough and has a flexible flap attached to each car and overlapping the car in front to prevent spillage during movement. The lead car has four wheels and tapered side drive plates in the front of the car to facilitate entry into the drive stations. The cars that follow have two wheels with a clevis hitch connecting the front to the rear of the car immediately forward. Movement of the train is provided by a series of appropriately placed drive stations having drive motors on either side of the track which are AC electric motors with drive means such as tires to provide frictional contact with the side drive plates. At each drive station, each drive motor is connected to an AC inverter and controller for drive control, with both voltage and frequency being modified as needed. The electric motors each turn a tire in a horizontal plane that physically contacts two parallel side drive plates external of the wheels of each car. Pressure on the side drive plates by these drive tires converts the rotary motion of the tires into horizontal thrust. The wheels on the cars are spaced to allow operation in an inverted position by use of a double set of rails to allow the cars to hang upside down for unloading. By rotating this double track system the unit train can be returned to its normal operating condition. Such a system is well known and commercially referred to as the Rail-Veyor™ material handling system.
Flanged wheels may be symmetrical to the side drive plates allowing operation in an inverted position which, when four rails are used to encapsulate the wheel outside loop discharge of the bulk material is possible. By using elevated rails, the train can operate in the inverted position as easily as in the convention manner.
Yet further, drives for such light rail systems have been developed as described in U.S. Pat. No. 5,067,413 to Kiuchi et al. describing a device for conveying travelable bodies which are provided no driving source, on a fixed path. A plurality of travelable bodies travels on the fixed path while aligned substantially in close contact with each other. Traveling power is transmitted to one of a plurality of travelable bodies which is positioned on at least one end of the alignment. The traveling power drives the travelable body with frictional force while pressing one side surface of the travelable body, and is transmitted to the travelable body while backing up the other side surface of the travelable body. A device to transmit traveling power is arranged on only a part of the fixed path. While light rail systems such as the Rail-Veyor™ material handling system above described are generally accepted, there is a need to provide an improved system having high efficiency and reliability with regard to controlling the movement of the train and in particular multiple trains with the bulk material transport system. The present invention is also directed to an improved system and method for controlling such light rail systems in an efficient and reliable manner.